var code ; //在全局 定义验证码  
function login()
{
	var username = document.getElementById("username").value;
	var password = document.getElementById("password").value;
	if(username!=null && username!="" && password !=null && password!="")
	{
		document.forms[0].action="login.action";
	}else
	{
		alert("用户名和密码不能为空！");
		document.forms[0].action="";
	}
}

function createCode()  
{   
  code = "";  
  var codeLength = 6;//验证码的长度  
  var checkCode = document.getElementById("checkCode");  
  var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');//所有候选组成验证码的字符，当然也可以用中文的            
  for(var i=0;i<codeLength;i++)  
  {                    
    var charIndex = Math.floor(Math.random()*36);  
    code +=selectChar[charIndex];                    
  }  
  if(checkCode) //这里不是很懂,有高手可以解释下  
  {  
    checkCode.className="code";  
    checkCode.value = code;  
  }    
}  
       
function validate ()  
{  
  var inputCode = document.getElementById("codeimg").value;  
  if(inputCode.length <=0)  
  {  
      alert("请输入验证码！");  
      document.getElementById("codeimg").focus();  
  }  
  else if(inputCode != code )  
  {  
     alert("验证码输入错误！");  
     createCode();//刷新验证码  
     inputCode = "";  
     document.getElementById("codeimg").focus();  
  }else{  
      document.frmRegister.submit();  
  }         
}  